strnlen - determine the length of a fixed-size string

       For an explanation of the terms used in this section, see attributes(7).
       ┌─────────────────────────────────────────────────────────────────────────────┬───────────────┬─────────┐
       │ Interface                                                                   │ Attribute     │ Value   │
       ├─────────────────────────────────────────────────────────────────────────────┼───────────────┼─────────┤
       │ strnlen()                                                                   │ Thread safety │ MT-Safe │
       └─────────────────────────────────────────────────────────────────────────────┴───────────────┴─────────┘

       The  strnlen()  function  returns  the  number  of  bytes  in  the  string pointed to by s, excluding the
       terminating null byte ('\0'), but at most maxlen.  In doing this,  strnlen()  looks  only  at  the  first
       maxlen characters in the string pointed to by s and never beyond s[maxlen-1].

       POSIX.1-2008.

       Standard C library (libc, -lc)

       strnlen - determine the length of a fixed-size string

       The  strnlen()  function  returns  strlen(s),  if that is less than maxlen, or maxlen if there is no null
       terminating ('\0') among the first maxlen characters pointed to by s.

strlen(3)

Linux man-pages 6.9.1                              2024-06-15                                         strnlen(3)

       POSIX.1-2008.

#include<string.h>size_tstrnlen(constchars[.maxlen],size_tmaxlen);

   Feature Test Macro Requirements for glibc (see feature_test_macros(7)):

       strnlen():
           Since glibc 2.10:
               _POSIX_C_SOURCE >= 200809L
           Before glibc 2.10:
               _GNU_SOURCE